1. Field
The disclosure relates to a method and a system for configuration of acousto-optic deflectors for laser beam scanning.
2. Background
Galvanometer based optical scanners are used to position optical beams for a broad range of industrial, scientific, imaging, and laser applications. Galvanometer based scanners may be referred to as “galvos”. A galvo system may be comprised of a galvanometer, one or more mirrors, and servo circuitry for driving the galvo system and controlling the positioning of the one or more mirrors.
Galvo based systems may be used for laser beam scanning and for laser drilling of vias in applications such as integrated circuit design. In integrated circuit design, a via is a small opening in an insulating oxide layer that allows a conductive connection between different layers. Galvo based laser drilling of vias is commonplace in the electronics industry, allowing high density circuits to be made for a range of products. In galvo based laser drilling of vias, laser beams are steered by mechanical movements of mirrors in a galvo based system to drill vias on an insulating dielectric layer or some other material.
The throughput rate for via drilling may be improved by increasing the galvo frequency and through other mechanisms. The galvo frequency is difficult to increase in view of limitations on the speed of mechanical mirror movement in galvo system. The mechanical movement of the mirror also makes it difficult to improve the accuracy of the positioning of the laser beam. As a result, galvo systems may be relatively slow and the accuracy of galvo systems may be limited.
An acousto-optic deflector may also be used to spatially control a laser beam. In the operation of an acousto-optic deflector, the power driving the acousto-optic deflector may be kept a constant level, while the acoustic frequency is varied to deflect the laser beam to different angular positions. In an acousto-optic deflector changes in the angle of direction and the angular position of the laser beam is linearly proportional to the acoustic frequency. If the acoustic frequency is higher, then the diffracted angle is larger.